A massive search was under way for an EgyptAir plane that disappeared over the Mediterranean with 66 people on board, with several countries joining the effort to find the jet.

The search intensified on Friday, a day after Egypt's aviation minister said that while it was too soon to say why the Airbus A320 flying from Paris to Cairo had vanished from radar screens, a "terrorist" attack would be a more likely scenario than a technical failure.

The tragedy raised fears of a repeat of the bombing of a Russian passenger jet by the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group over Egypt last October that killed 224 people.

The Egyptian Investigation Team in co-operation with the Greek counterpart are still searching for other remains of the missing plane.

Both Egypt and Greece dispatched aircraft and naval vessels to join the search. They were expected to be joined by French teams, while the US sent a surveillance plane to help with the operation.

Egypt's President Abdel Fattah el-Sisi demanded an "intensified search" for the aircraft after reports that wreckage had been found were retracted.

Conflicting reports

EgyptAir initially said on its Twitter account that the Egyptian authorities had recovered wreckage from the missing aircraft, but the head of the Greek air safety authority told the AFP news agency that debris found close to the area where the jet went down did "not come from a plane".

French President Francois Hollande said the plane had "crashed", as authorities in Paris and Cairo opened investigations.

Egypt's Aviation Minister Sherif Fathy said he was unable to "deny the hypothesis of a terrorist attack or something technical".

Richard Marquise, a former FBI agent who led the US task force investigating the Lockerbie bombing, said that Egypt was quick to point to an attack, unlike France.

"It's becoming a game of finger pointing about who's responsible, whether it's mechanical failure of EgyptAir, or a terrorist bomb on the aircraft," he told said.

He added that this was in contrast to the October 2015 Metrojet bombing, when Egypt was more reluctant than Russia to point to a possible attack. In that case, Egyptian authorities were responsible for security as the city of Sharm el Sheikh was the departure point.

In the EgyptAir case, French authorities were responsible for security as the plane left from Paris.

EgyptAir said passengers included: 30 Egyptians; 15 French; two Iraqis; one Briton; one Belgian; one Sudanese; one Chadian; one Portuguese; one Algerian; one Canadian; one Saudi and one Kuwaiti. They included a child and two babies.

Both France and Egypt have come under attack by ISIL fighters in the past year, and Hollande promised a comprehensive probe into the cause of the crash.

ISIL has been waging a deadly insurgency against Egyptian security forces and last October claimed the bombing of the Russian airliner flying home holidaymakers from the Egyptian resort of Sharm el Sheikh.

'Too early to say'

In the United States, White House spokesman Josh Earnest said: "It's too early to definitively say what may have caused this disaster."

The incident also became an issue in the US presidential election campaign, where national security has become up a hot topic.

Presumptive Republican presidential nominee Donald Trump said it appeared to be "yet another terrorist attack.

"When will we get tough, smart and vigilant?" he said.

His likely Democratic opponent Hillary Clinton agreed that it "does appear that it was an act of terrorism" and "once again shines a very bright light on the threats that we face from organised terror groups".